1. Field of the Invention
The present invention relates to a round baler for fibrous agricultural material such as hay, straw and silage and including a plurality of compression elements, delivery elements, drive means for driving the same and including a main drive and chain or belt means connecting the main drive with respective elements, and at least one wrapping apparatus for binding compressed bales.
2. Description of the Prior Art
Round baler with a cutting section, in which the picked up stem crop is chopped by a plurality of blades engageable with the conveying rotor to a greater or less extent before compression, find an increasingly greater application, in particular for use in forming silage bales. Up to the present, usually from 3 to 14 blades were used, however, the tendency is to use from 20 to 30 blades to achieve even a greater compression density. This can substantially increase the power demand of the round balers. In extreme cases, the power demand of round balers with a cutting section can be twice as large as that of round balers without a cutting section.
Thus, the prospectus Roll Presses RP 200, Publication 8.96, describes round balers in which the main drive chain from a tractor to the main drive of the baler is protected from an overload, and in which a so-called cam clutch, e.g., such as Fabrikats Walterscheid K64, is provided in front of the main drive and turns off the entire drive of the baler in case the entire torque of the baler exceeds a predetermined magnitude.
The use of this well known cam clutch is accompanied by two serious drawbacks:
If a baler is protected by setting actuation of the cam clutch at a torque value which provides for optimal density of a short-cut stem crop, the use of a baler without a cutting section leads to a too high drive torque applied to the compression elements and their drives, which, considering that almost the entire drive power, except a relative small amount required by the pick-up means (about 2-3 kw) is spent for driving the elements located the bale chamber, can result in a destruction of these drives and/or the compression elements. PA1 Upon actuation of the cam clutch, the entire drive of the baler is turned off, and the bales remain in the bale chamber. Restart of the baler is often become impossible. To do this, the bale chamber is opened and unloaded. Only then the drive of the baler is restarted. A particular disadvantage of this consists in that the unbound content of the bale chamber is removed which can be bound only with great difficulties. Balers with limited hydraulic opening of the bale chamber are described in Prospectus Class Rollant 66,46 silage, 46 Roto Cut, Publication August 1995.
The drawback of this solution consists in that oversized bales are not suitable for being wrapped with a foil in a foil wrapping machine, and often should be cut and "overpressed."
European Publication EPO 150 629 B1 discloses a round baler in which a torque indicator is mounted on the main drive shaft and controls the tensioning device for the belts. When drive torque exceeds a certain threshold, the belts are somewhat slackened. The use of the torque indicator permits to reduce the response frequency of the slipping clutch in the main drive shaft during pick-up of swath accumulations.
Accordingly, an object of the present invention is to provide means for preventing an overload of compression elements and their drives, in particular, under different operational conditions, e.g., with or without use of cutting sections.